共查询到20条相似文献,搜索用时 15 毫秒
1.
J. A. Brown R. H. Heffner M. Leon D. M. Parkin M. E. Schillaci W. B. Gauster A. T. Fiory W. J. Kossler H. K. Birnbaum A. B. Denison D. W. Cooke 《Hyperfine Interactions》1979,6(1-4):233-236
Data are presented for the temperature dependence of the muon depolarization rate between 10 K and 120 K for three samples of niobium of varying. purity. Two samples, each containing approximately 200 ppm substitutional Ta and interstitial concentrations of 10 ppm and 560 ppm (mostly O), respectively, were studied. A third sample containing only 3 ppm Ta and an estimated 10 ppm total interstitial impurities was also measured. The results indicate that even at the lowest temperatures studied the depolarization of the muon is dominated by traps associated with impurities.This work was supported by the U. S. Department of Energy 相似文献
2.
T. Aurenz K. -P. Arnold K. -P. Döring M. Gladisch N. Haas D. Herlach W. Jacobs M. Krause M. Krauth H. Orth H. -E. Schaefer K. Schulze A. Seeger 《Hyperfine Interactions》1984,17(1-4):191-196
The transverse spin relaxation of positive muons (
+) has been measured on Nb and Ta after irradiation with 3 MeV electrons. In high-purity Nb the
+ diffusivity derived from the trapping at irradiation-induced defects above 100 K is explained in terms of adiabatic hopping. At lower temperatures there is evidence for the dominating processes to be fewphonon incoherent tunnelling and coherent hopping. Annealing results in the formation of new defects capable of trapping the
+. In Ta at least two types of irradiation-induced defects capable of trapping
+ survive up to annealing temperatures of 400 K. 相似文献
3.
N. Haas D. Herlach W. Jacobs H. -J. Mundinger J. Rosenkranz H. -E. Schaefer M. Schmolz A. Seeger K. -P. Döring K. Fürderer M. Gladisch 《Hyperfine Interactions》1986,31(1-4):217-222
The transverse spin relaxation of positive muons has been measured on an Al single crystal and on polycrystalline In after
irradiation with 2 MeV electrons at 9 K or 11 K, sample transfer at 4.2 K, and various subsequent annealing treatments. The
Al data are analysed in terms of diffusion-limited trapping by vacancies. This yields a muon diffusivityD
μ which within experimental accuracy is proportional toT between 4 K and 50 K, indicating that in this temperature intervalD
μ is dominated by one-phonon-assisted incoherent tunnelling. In In only very small effects due to the irradiation could be
observed. The muons appear to be localized in octahedral interstices. From the motional averaging taking place above about
20 K the diffusivity ofD
μ in In is deduced. 相似文献
4.
J. Kondo 《Hyperfine Interactions》1986,31(1-4):117-133
The hopping rate W of the positive muon in metals is studied theoretecally. We consider four interactions: muon-electron interaction,
linear as well as quadratic muon-lattice interactions and inhomogeneous broadening of the muon levels due to imperfections.
The W-vs-T curve consists of four regions. The highest-T region, where the small polaron theory is applicable, is followed
by a minimum, below which the Kagan-Klinger damping may be dominant. Then, the damping due to metallic electrons dominates
and the hopping rate obeys a power law of a negative power. When kT is smaller than the inhomogeneous broadening, the hopping
rate obeys another power law of a positive power, as Sugimoto has shown. We analyze experimental data on muon diffusion in
Cu, Al and Fe. 相似文献
5.
《Physics letters. A》1987,122(1):56-60
Iron doped with 400 ppm Ti was investigated by the muon spin rotation method. Below 70 K and above 180 K the normal 50 MHz signal of pure Fe was observed. However, in a small temperature range around 100 K a completely different frequency with v = 112 MHz shows up. This signal is attributed to muons trapped at Ti in Fe. The experiment yields the hyperfine field Bhf and the binding energy EB for the trapped muons. We find Bhf = 93(5) mT and EB = 81(5) MeV. 相似文献
6.
M. Soetratmo H. Natte R. Hempelmann O. Hartmann R. Wäppling M. Ekström 《Hyperfine Interactions》1997,105(1-4):245-252
A systematic μSR study on nano‐Cu has demonstrated that the diffusion of μ+ in nanocrystalline metals is influenced by both features of the nanostructure, i.e., by the very small grain size and by
the comparatively large fraction of grain boundaries. The former feature yields a size effect of the phonon‐assisted muon
tunneling, but only at particle diameters below 20 nm. The latter feature, in samples with crystallite sizes above 20 nm diameter,
i.e., with bulk diffusional behaviour, establishes a connection between μ+ diffusion coefficient and particle size: if one of these quantities is known, the other could be evaluated.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
7.
A. Weidinger 《Hyperfine Interactions》1984,17(1-4):153-166
This paper gives a summary of the results obtained by the Konstanz group on electron-irradiated iron. The main achievement was the observation of a number of different frequencies in Fe, which could be assigned to isolated vacancies and to vacancy-impurity pairs. The annealing behaviour of these frequencies was studied. In the present paper, the framework for the analysis of the data and the main conclusions are reviewed. 相似文献
8.
G. M. Luke J. H. Brewer S. R. Kreitzman D. R. Noakes M. Celio R. Kadono E. J. Ansaldo 《Hyperfine Interactions》1991,64(1-4):721-727
We have studied the quantum diffusion of positive muons in pure copper over the temperature range 12 mK≤T≤150 K using weak longitudinal field μSR. Below 150 K, this technique has proved to be the most sensitive to the muon hop
rate. Our final results for the behaviour of the muon hop rate are well explained within the framework of theories for the
quantum diffusion of light interstitials in metals of Kondo, Yamada and others. In addition, the use of level-crossing resonance
has allowed us to measure the electric quadrupole interaction strength (and sign) of the copper nuclei, ωQ= −3.314(7) μS−1. These results have enabled us to show that the muon occupies the same octahedral site at all the temperatures studied, ruling
out the possibility of metastable muon sites contributing to any significant portion of the muon polarization. 相似文献
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11.
S. F. J. Cox R. M. Macrae D. S. Sivia N. Ayres De Campos P. J. Mendes J. M. Gil 《Hyperfine Interactions》1994,85(1):67-72
Longitudinal muon spin relaxation is measured in ice, using samples with and without enrichment in H2
17O, with a view to studying the mobility of the muonium fraction. A conventional analysis of the data, on the assumption that relaxation of the diamagnetic fraction is negligible, suggests that more than one mechanism of muonium relaxation is at work. A Bayesian analysis warns that separation of the diamagnetic and paramagnetic signals may not be so straightforward. 相似文献
12.
J. M. Welter D. Richter R. Hempelmann O. Hartmann E. Karlsson L. O. Norlin T. O. Niinikoski D. Lenz 《Zeitschrift für Physik B Condensed Matter》1983,52(4):303-313
Transverse field SR experiments were performed on several different samples of copper in the temperature range below 2K, including isotope separated copper, Fe and Si doped polycrystalline copper and monocrystalline copper. No strong isotope dependent effect was observed. A63Cu and a natural copper sample of identical purity both yield 0.16 s–1 for the low-temperature plateau, while an increased linewidth inthe65Cu case may be related to the strong effects of Fe impurities. Careful transverse field measurements on large single crystals at 0.08K reveal non-Gaussian lineshapes in accordance with the picture of diffusing muons at this temperature. This allows us to reject several of the existing models for muon behaviour in copper below 2K. 相似文献
13.
O. Hartmann E. Karlsson R. Wäppling A. Gustavsson-Seidel D. Richter R. Hempelmann W. J. Kossler B. Hitti J. Kempton W. F. Lankford C. E. Stronach 《Hyperfine Interactions》1986,31(1-4):241-245
We have studied the muon diffusion in various Nb−HX systems with 0.75<x<0.95, with special attention to the concentrations x<0.9. For x>0.9 the muon linewidth as function of
temperature has a smooth behaviour and the muon mobility is strongly correlated to the hydrogen diffusion in the beta phase.
The activation energy for the μ+ diffusion is 160 meV, which is lower than that for protons. At hydrogen concentrations below 0.9, the muon diffusion behaviour
is more complicated, and the influence of Nb−H phase transitions is evident. The implications for the local environment of
the muon are discussed. 相似文献
14.
Hydrogen diffusion in the ordered hydride β-V2H is mainly brought about by a minority fraction of interstitial atoms on antistructural sites. Recently, this mechanism was
elucidated in a single crystal QNS study at temperatures close to the critical point (390 K≤T≤440 K) where already an appreciable amount of antistructural sites is occupied. Here we use the positive muon as a radioactive
hydrogen tracer in order to show that the same diffusion mechanism is also valid at low temperatures (80 K≤T≤320 K) where the different jump processes are very slow and where the fraction of antistructural atoms is tiny but nevertheless
dominates the long range diffusion. 相似文献
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17.
The broad emission line at about 1.512 eV, which dominates the emission spectra of pure GaAs at intermediate excitation levels (1–300 kW/cm2) and low temperatures (<40 K) is investigated in magnetic fields up to magnetic flux densities of 10 T. The shift of the emission maximum in the magnetic field is exactly the same as recently reported for the free exciton. This demonstrates that at high excitation levels exciton-electron scattering is the dominant mechanism for the radiative decay of free excitons. 相似文献
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19.
Muon captures by nucleon pairs via meson-exchange currents produce a high energy excitation tail in heavy nuclei. The muon induced fission by these excitations is calculated in several subactinide nuclei with high threshold fission barriers. The probability for delayed fission ranges from 4×10?5 to 4×10?3 for the isotopes considered. 相似文献
20.
S. J. Blundell 《Applied magnetic resonance》1997,13(1-2):155-164
Muon spin rotation (μSR) experiments can be especially helpful in the study of various organic molecular materials. The technique has been used to study the magnetization in nitronyl nitroxide organic ferromagnets, the spin-density-wave ground state in various charge transfer salts, the dynamics of carriers in organic conductors and the vortex structures in organic superconductors. I outline the motivation for studying these new materials and review and discuss the results of recent work. 相似文献